THE DIFFERENTIATION OF CARBOXYLIC ACID AND THEIR DERIVATIVES USING CLASSIFICATION TESTS Kim Genesis DR. Tuazon, Carl Ubana, Anjelica Versoza, Karen Faith Villaflores, Villaflores, Jeremiah Jan M. Vivar Group 8 2D Pharmacy Organic Chemistry Laboratory ABSTRACT The experiment tested compounds to differentiate reactivity of carboxylic acids and disti nguish carboxylic acid using classification tests. The four tests were as follows, Hydrolysis of Acid Derivatives using acyl halides and acid anhydrides, esters and amides this test was to know if the sample has u ndergone hydrolysis hydrolysis by comparing temperatures, precipitates and the evolution of gas; Alcoholysis or the Schotten-Baumann Reaction using aceti c acid and acyl halides and acid anhydrides for testing this test was to know if the sample has undergone hydrolysis with the compounds given, odor and formation of layers were compared; Aminolysis or the Anilide formation was the third test, it used acyl halides and acid anhydrides to observe if it has undergone aminolysis we observed a white precipitate; Hydroxamic Hydroxamic Acid Test using Ethyl acetate and acetamide, observed in this test was a yellow solution for the preliminary test and a deep burgundy in the addition of 5% FeCL
INTRODUCTION
EXPERIMENTAL
Carboxylic acids and their derivatives are organic compounds containing the acyl group core structure attached to a Y group, which may be an electronegative atom or a substituent. This experiment aims to Differentiate the reactivities of carboxylic acids and to distinguish carboxylic acids using classification tests. [1] Carboxylic acids are organic compounds that have a carboxyl group attached to an aryl group (ArCOOH). The ‘R’ may be a hydrogen and the result is formic acid. They may be mono carboxylated, multi carboxylated, substituted (hydroxyl groups) or they may be aromatic. Physical properties of carboxylic acids are as follows; Low molecular weight carboxylic acids are soluble in water and therefore lie in class S 1. Water insoluble acids dissolve in both sodium hydroxide solution and sodium bicarbonate solution, being classified as under class A1. When they react with sodium bicarbonate, they evolve carbon dioxide gas. This is considered as a good simple indication of them. The reactions of carboxylic acid in chemical means is related to: the proton as in salt formation reactions, removal of the hydroxyl group as in conversion to derivatives such as esters, amides or acid chlorides, substitution either in the alpha position of aliphatic acids or in the meta position of aromatic ones.
A. Compounds Tested: Acetyl chloride, Acetyl anhydride, Ethyl acetate, Benzamide, Acetic acid, Acetamide. Structural formula of the compounds used: 1. Acetyl Chloride
2. Acetyl Anhydride
3. Ethyl Acetate
4. Benzamide
5. Acetic Acid
6. Acetamide
B. Procedure 1. Hydrolysis of acid derivatives a. Acyl halides and Acid Anhydrides 1 ml of water was placed in a test tube. 10 drops of acetyl chloride/acetic anhydride were added to the test tube with 1 ml water. The resulting mixture was divided in to two portions. In the first portion, 1 ml of 2%AgNO3was added. In the second portion, 1 ml of saturated NaHCO3 was added. b. Esters 2 ml of 25% NaOH solution was added to 1ml of Ethyl acetate. the mouth of the test tube was covered with a marble and then subjected to a boiling water bath for 5minutes. The sample was neutralized with 10% HCl solution c. Amides 1ml of benzamide was treated with 5ml of 10% NaOH solution and was heated to boiling. Litmus paper was then held against the mouth of the test tube 2. Alcoholysis: Schotten – Baumann Reaction A mixture of 10 drops of acetic acid, 1 ml ethanol and 5 drops of conc. H 2SO4 was heated till warm and subjected to a water bath for 2 minutes. 0.5 ml of ethanol, 1ml of water and0.2ml of acyl halide or acid anhydride sample are put in another test
tube. In the mixture was added 2ml 20% NaOH solution. A cork or parafilm were used as stopper for the test tube and was shaken for several minutes. 3. Aminolysis: Anilide Formation A few drops of acetyl chloride or acetic anhydride sample were added to 0.5mlaniline and was transferred to a new test tube containing 5ml water. 4. Hydroxamic Acid Test Preliminary test: 2 drops of the sample were mixed with1ml of 95% ethanol and 1M HCl. 1drop of 5% FeCl 3 was added to the solution. It is noted that if another color other than yellow is obtained, the test would not be used. Otherwise, the test is conducted as follows: 2 drops of the sample were added to 2ml of alcoholic NH 2OHHCl and ml of 1M KOH. The solution was heated in a boiling water bath for 2 minutes. After which it was cooled and then 1ml of 5% FeCl3 was added.
RESULTS AND DISCUSSION Table 1. Hydrolysis of Acid Derivatives Observations Acyl halides and Acid Anhydrides
Acetyl Chloride Acetic Anhydride Ester: Ethyl Acetate Amide
Warming effect
Upon addition of 2% AgNO3
Warming Whit ppt, effect AgCl 3 No No ppt warming effect Odor: Vinegar like
Upon addion of saturated NaHCO3 Evolution of Gas, CO2 Evolution of Gas, CO2
Red to Blue litmus paper
The acid halides and anhydrides acetyl alcohol and acetic anhydride both showed evolution of CO2 when NaHCO 3 was added. Upon addition of water andAgNO 3, Acetyl chloride showed warming effect and a white cloudy precipitate, respectively; however acetic anhydride did not show both warming and precipitate. The Ester, Ethyl acetate, after neutralizing with10% HCL and water bathing, expressed a Fruity/Plastic-balloon like odor The Amide, Benzamide, upon
heating turned basic, indicating presence of ammonia with amine like odor.
Table4. Hydroxamic acid test
Observations Preliminary test Ethyl acetate Acetamide
Figure1. Equations for Hydrolysis of Acid Derivatives Table2. Alcoholysis: Schotten- Baumann Reaction
Acetic acid Acyl halides and acid anyhydrides Acetyl chloride Acetic anhydride
Observations Odor: Plastic-balloon like odor Odor Formation of layers Plastic balloon No layer formed like Fruity odor No layer formed
The carboxylic acid, acetic acid, upon water bathing for 2 minutes exhibited plastic balloon like odor, but no layer was formed Acyl halide, Acetyl chloride after addition of 20% NaOH solution and agitation, exhibited also aplastic balloon like odor and formation of no layers.
Figure2. Representation of Alcoholysis Table3. Aminolysis: Anilide Formation
Observations Acyl halides and acid Appearance of precipitate anhydrides Acetyl chloride White precipitate Acetic anhydride White precipitate
Acetyl Chloride and Acetic Anhydride exhibited formation of white precipitate upon addition of 0.5ml aniline.
Yellow solution Yellow solution
Upon addition of 5% FeCl3 Deep burgundy Deep burgundy
A Preliminary test was done to eliminate those phenols that give color with ferric chloride in acidic solution that would therefore give false positive result in the ferric hydroxamic test. Ethyl acetate ande Acetamide yield deep burgundy color which was a positive result. REFERENCES: [1] Jaism, A., Mohammad, D. (2012) A Laboratory manual on practical organic chemistry for second year students. University of Baghdad. Pavia, D., Lampman, G., Kriz, G., & Engel, R. (1998). Introduction to organic laboratory techniques: a microscale approach.3rd Ed. USA: Saunders Publishing Comapany. Williamson, K; Minard, R; Masters K. (2007). Macroscale and microscale organic experiments. 5th Ed. Boston, USA: Houghton Mifflin Company. Garner, CM. (1997). Techniques & experiments for advanced organic laboratory. USA: John Wiley & Sons. Inc. MACAULAY, DB. (2007). General, organic & biological chemistry an integrated approach. USA: John Wiley & Sons. Inc.
